One of these organisms was the basis of the rII system used by Benzer for single nucleotide mapping,
 and the cosmid uses elements derived from one of these organisms. The fir
One of these organisms was the basis of the rII system used by Benzer for single nucleotide mapping,
 and the cosmid uses elements derived from one of these organisms. The first stretch of DNA ever
 sequenced by Frederick Sanger was from one type of this organism, dubbed phi X, and the Luria-Delbruck
 experiment used them to show that mutations are spontaneous. Another experiment using them labeled
 their DNA with phosphorus-32 and their proteins with sulfur-35 in order to show that nucleic acids are the
 material of heredity; that experiment was performed by Hershey and Chase using the T4 type. For 10
 points, name these viruses which infect bacteria.
One of these organisms was the basis of the rII system used by Benzer for single nucleotide mapping,
 and the cosmid uses elements derived from one of these organisms.
{bacteriophage} [prompt on {viruses}]